Pressed for answers, Lohan says upcoming stint at a rehab facility is a “blessing.”

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Lindsay Lohan talks to David Letterman about her upcoming trip to rehab, her guest star roles in the series "Anger Management" and her film "Scary Movie 5" and more during the "Late Show with David Letterman."

Updated at 8:06 AM EST on Wednesday, Apr 10, 2013

Lindsay Lohan was on “Late Show with David Letterman” Tuesday night, and she got grilled. Letterman didn’t waste much time getting to what was on everybody’s mind: Lohan’s upcoming trip to rehab.

At times things got a bit awkward and tense. But there was also fun to be had. In fact, the jokes started during Letterman’s monologue. “People have been coming up to me asking why Lindsay Lohan is on the show tonight,” Letterman said, pausing for effect. “She believes I’m Dr. Phil.”

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A little background is necessary here: In March, because she had violated her probation, Lohan agreed to spend 90 days at a rehab facility.

Not long after Lohan came on stage and sat down, Letterman asked her, “Aren’t you supposed to be in rehab now?”

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For a moment there, the air felt a bit tense, and Lohan replied, “Do you not watch anything that goes on?” She told Letterman she’ll be starting rehab May 2. And how many times has she already been in rehab? “Several,” she said.

“How will this time be different?” Letterman asked. “What are they rehabbing? What is on their list?” Lohan sat in silence, biting her lip, obviously wishing to talk about something else, like “Scary Movie 5,” which she was here to promote.

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Lohan said she’s “happiest and healthiest” when she’s working and that her upcoming stint at a rehab facility is a “blessing.”

And just when you thought it was over, it wasn’t. “Is it alcohol?” Letterman asked. Lohan assured him that they had discussed this in the past, to which Letterman replied, “Now I’m the one who’s having the blackout.”

But Lohan also got into the act, sipping from her “Late Show” mug, acting surprised there was no vodka in there.

Letterman ended his interview with Lohan the way he began it, by taking her hand into his and giving it a kiss. “God bless you,” he said. “Good luck to you.”